The present invention relates to a damper and, more specifically, a damper in which a piston with orifice slides in a cylinder filled with a viscous fluid.
In order to prevent a sound of sudden closing of a cabinet door and the like, a damper is provided in a doorstop portion of a cabinet for reducing a closing speed of the cabinet door.
As the damper for generating a braking force mentioned above, there has been known a damper including: a cylinder filled with a viscous fluid; a piston dividing inside the cylinder into two portions in an axial direction and including an orifice communicating in the axial direction; and a piston rod connected to the piston. The damper generates the braking force (damping force) through resistance of the viscous fluid passing through the orifice when the piston moves together with the piston rod inside the cylinder in the axial direction (see Patent Reference No. 1).
Patent Reference No. 1: Japanese Patent Publication (Kokai) No. 3465978.
The above-mentioned damper uses a characteristic wherein flow resistance of a viscous fluid progressively increases with a moving speed of a piston. For example, when a damper is provided in a door for absorbing a shock, small resistance acts on a slow closing-door operation and large braking force acts on a sudden closing-door operation.
A diameter of the orifice provided in the piston is adjusted to control the braking force. When the control force during a low speed is set appropriately, the braking force during a high speed may become too small. On the other hand, when the braking force during the high speed is set appropriately, an operational performance during the low speed may be lowered. Specifically, it is difficult to have a wide dynamic range of the braking force.